Friday, December 29, 2006

Tigers Fielding Analysis for 2006

Today, I’m beginning a series of posts looking at individual fielding statistics for the Tigers and the rest of baseball in 2006.It is more difficult to measure fielding than hitting or even pitching so I will discuss several different options.I will start with the most basic of fielding stats and work my way up to the more sophisticated modern methods.Finally, I will rank the players at each position by aggregating all the stats.Today I’ll give a brief history of fielding stats and a discussion of the most frequently used measures.After that, I’ll show how the Tigers rank on these measures.In future posts, I’ll discuss some of the newer fielding measures.

The most commonly reported fielding measure is fielding percentage (FPCT) which is the infrequency with which fielders make errors on balls which they reach. It is calculated as (Total plays – errors)/total plays. Not making errors is a positive thing so this statistic has some value. It has also some important flaws though. First, errors are subjective and judgement varies from one official scorer to the next.

More importantly, FPCT says nothing about range. Some players get to a lot of balls which other players can not reach. Measurement of range is an area of sabermetrics which is still developing. The two most accessible range statistics, Range Factor (RF) and Zone Rating (ZR), are discussed below.

Range Factor (RF) was originated by Al Wright in the 1870s but it was virtually ignored for over 100 years until Bill James re-introduced it around 1980. Range Factor = (put outs + assists)/games. One of the limitations of RF is that it is a team dependent statistic. For example, an outfielder playing behind a predominantly groundball staff will have fewer opportunities than an outfielder on a staff with a lot of fly ball pitchers. Similarly, the range factors of all fielders on a team will be affected if their pitchers strike out a lot of batters.

Zone Rating (ZR) was developed by STATS, Inc in the early 1990s. They divided the baseball field into zones and assigned the zones to different fielders. Zone rating is the percentage of balls hit into a player’s zone which are turned into outs. One of the problems with zone rating is that it depends on the reliability of those collecting the data. They need to judge whether balls were actually hit into the zone and distinguish between fly balls and line drives as there is a different zone for each. Another drawback of zone rating is that it treats all balls in the zone the same way even though it may be more difficult to reach some balls within the zone than others.Since Zone Rating penalizes a player for errors by considering them to be missed opportunities, it essentially makes FPCT obsolete.

Table 1Shows how Tiger fielders Rank on FPCT, RF and ZR.Fielding percentage does not tell us much about fielding performance but has been included on the table to show how deceptive it can be in evaluation of fielding.The discrepancies between range factor and zone rating, two statistics which are supposed to measure the same thing tell us they are not completely reliable. zone rating is considered to more reliable because it is not as team dependent.

Based on range factor and zone rating, Sean Casey (7th in RF and 4th in ZR) and Chris Shelton (3rd, 1st) both ranked quite well among 27 first basemen with 600 or more innings.Range does not work as well for first basemen as it does for other fielders because it does not address throws taken from infielders and this is obviously an important part of their jobs.Still, it is somewhat surprising that they did so well.It will be interesting to see how they do on other metrics as I get to them.

So, as many of us observed, the Tigers apparently had strong infield and center field defense but were not as good at the corner outfield positions.These statistics don’t really pertain to catchers so they will have to be addressed at another time.